Dichloro- and trichloroacetyl chloride are intermediates in chemical synthesis. For example, the herbicides, which are described in the International Application WO 93/24483 dated Dec. 9, 1993 (Chemical Abstracts 120, 1994, Reference 245064y) and which are particular pyrrolidone compounds, can be synthesized using dichloroacetyl chloride. Trichloroacetyl chloride can be used to synthesize trifluoroacetyl chloride, which represents, in turn, a pharmaceutical and agrochemical intermediate. This is disclosed in the French Patent Application 2,592,376 dated Jul. 3, 1987 (Chemical Abstracts 108, 1988, Reference 94077d).
The synthesis of di- or trichloroacetyl chloride by photochemical oxidation of trichloroethylene or tetrachloroethylene with oxygen in the presence of chlorine while irradiating with short-wave light in the liquid phase, is known from the German Patent 759 963. The oxidation of tetrachloroethylene through quartz glass in the presence of chlorine while irradiating with light having a wavelength of 436 nm (=436 m.mu.) with formation of CCl.sub.3 C(O)Cl is described by Schott and Schumacher in Z. Phys. Chem. 49 (1941), pages 107 to 125 and the corresponding oxidation of trichloroethylene is described in Z. Phys. Chem. Section B, 37 (1937), pages 365 to 373. However, according to that patent, the photooxidation in the gas phase can be carried out only on a very small scale because of the high evolution of heat and the difficulty of dissipating the heat from the gaseous products; consequently, the experts turned to liquid phase oxidation (already for the method of the German patent 759 963). As disclosed in the European patent EP-B-O 422 520, however, epoxides are formed to a greater extent by liquid phase oxidation. According to the European patent, the starting material is passed in a thin film through the reaction zone. A further improvement in the liquid phase method is the objective of the European patent application EP-A-O 623 578 dated Nov. 9, 1994. For that method, in which trichloroethylene is reacted with oxygen in the liquid phase in the absence of chlorine with irradiation with short-wave light, certain nitrogen-containing bases (secondary amines) are added, in order to accelerate the conversion of epoxides, which are produced as a by-product, into dichloroacetyl chloride. The addition of such a catalyst, which of course must be removed once again from the reaction mixture or product, greatly complicates the method.
Chlorodifluoroacetyl chloride is also an intermediate in chemical synthesis, for example, for the production of dyes. It is possible to trifluoromethylate alkyl and aryl halides by means of a derivative of chlorodifluoroacetyl chloride, namely by the methyl ester, in the presence of potassium fluoride and copper iodide. The aforementioned methyl ester is also an intermediate for the synthesis of difluorocarbene (G. A. Wheaton and D. J. Donald in J. Fluorine Chem. 8 (1976), pages 97 to 100). Difluorocarbene is used for the production of insecticides (EP-A 198 791 (U.S. Pat. No. 4,701,563)). The production of trifluorocarbene from trifluoromethyl phenyl mercury and other compounds of this type is a problem from environmental points of view.
The German Offenlegungsschrift 43 42 601 A1 discloses the production of, among other compounds, chlorodifluorodiacetyl chloride by the photochemical oxidation of 1,1-difluoro-1,2,2-trichloroethane under activating irradiation in the gas phase without the addition of sensitizers. The German Offenlegungsschrift 44 20 763 A1 discloses a corresponding method with the addition of elementary chlorine as sensitizer and irradiation with light having a wavelength .lambda..gtoreq.290 nm. The German Auslegeschrift 1 069 173 discloses, among other things, the production of chlorodifluorodiacetyl chloride from 1,1-difluoro-2,2-dichloroethylene or from 1,1-difluoro-1,2,2-trichloroethane or 1,1-difluoro-2,2,2-trichloroethane by photochemical oxidation. If the starting material is a saturated ethane derivative, the reaction for this embodiment should advisably be carried out in the presence of chlorine.